On a map, a closed shape defined by a connected sequence of x,y coordinate pairs, where the first and last coordinate pair are the same and all other pairs are unique.

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7
votes
3answers
826 views

Lossless Polygon Simplification?

Is there a standard/recommended algorithm for simplifying a polygon without shrinking any of its original boundaries? Right now I'm using TopologyPreservingSimplifer within JTS and running into ...
1
vote
3answers
971 views

“Identity” overlay in QGIS?

I have two polygon layers I'd like to overlay using QGIS or another open source tool. What I want as output is a polygon layer with the extent of one polygon, but with each polygon in that layer ...
1
vote
0answers
795 views

How to get polygon coordinates for Google Map from .poly files (preferably in nodejs)?

I have .poly files with polygons of countries. I want to use those polygons to make Google Map polygon layers. How may I read lng and lat points of polygons from those poly files? They look like these:...
0
votes
1answer
1k views

ARCGIS 10- Cutting down a tiff file layer to a smaller polygon?

I have a dynamic land map featuring open forest, closed forest ect of an area which is a tiff layer file. I want to be able to cut the layer file to my area of interest, the polygon I created? I also ...
1
vote
0answers
63 views

Delete polygon underlap?

I am editing a layer in QGIS with severe polygon overlaps. Is there a way to delete the underlapping portions (i.e. the invisible parts) using QGIS? If I import the layer into GRASS using the GRASS-...
4
votes
1answer
162 views

Postgis 2.0 geographic polygon has max longitudinal range

My problem is that I have a load of geographic point data (srid 4326) in a table. A user may do a bounding box search - essentially create a polygon as follows: l_poly geography(Polygon,4326):= '...
4
votes
1answer
482 views

intersection between two multipolygons yielding anomalous GeometryCollection object full of LineString's & Polygon's (trying to get intersect area)

Normally when I call the #intersection method on a multipolygon to find the intersection shape on another multipolygon I get a multipolygon returned back to me. Either that or something else I can ...
1
vote
1answer
744 views

JTS Polygon simplification without holes

I have a set of polygons without holes. I wish to merge any intersecting polygons. I don't want to have any holes in my simplified polygons. Is there a recommended way to achieve this using JTS? The (...
5
votes
1answer
612 views

Create MultiPolygon from QgsGeometry.fromMultiPolygon

I have a list of polygons' points like [[x1,y1],[x2,y2],[x3,y3],[x4,y4]] [[x5,y5],[x6,y6],[x7,y7].[x8,y8]] now I want to create multipolygon from it by using feature = QgsFeature() feature....
9
votes
2answers
3k views

How to remove small “salt & pepper” polygons from a layer?

I have a map made up of multiple polygons, with a few hundred thousand points very small polygons on within it. I need the larger polygons, but not the points small polygons. How do I select and ...
9
votes
4answers
22k views

How to Merge/Dissolve Polygons By Common Attribute Field in QGIS?

I have joined corresponding Local Enterprise Partnerships table data into a polygon shape file containing UK Local Authorities. How do I Dissolve or Merge the the Local Authorities polygons by ...
1
vote
0answers
61 views

Dissolving overlapping polygons - issue in QGIS [duplicate]

I have the OS Code-Point map which I want to dissolve into the regions that my company use. I have used the dissolve function in QGIS, but it is having a problem where a vertical street overlaps with ...
1
vote
1answer
146 views

How to find out to which polygon each points belongs to?

I have searched for an answer to this, but couldn't find anything useful. I have got a shapefile consisting of a number of polygons, and another shapefile with a number of points. I want to add a ...
1
vote
2answers
311 views

QGIS point sampling tool really slow for polygons?

I have a large field of randomly distributed points (100,000 of them to be precise), and I'd like to get values for a variety of raster and polygon coverages for each point. I've been using the QGIS ...
4
votes
1answer
129 views

What is the best format to encode polygons such as lakes?

I am looking for a standard format to encode polygons, such as lakes, in one file that is easy to create and common so that others can use it in different GIS systems. Every file will contain data on ...
4
votes
4answers
1k views

Creating polygons as % of original area using ArcGIS Desktop?

I have a polygon shapefile and need to create new polygons, within the originals, as % of original area. I used buffer by field (Field= new area as %) but the buffers are created in circles around ...
1
vote
1answer
2k views

Get Features from OpenLayers Layer.Vector not working

polygon_layer = new OpenLayers.Layer.Vector("Polygone", { projection : projLonLat, strategies : [ new OpenLayers.Strategy.Fixed() ], protocol : new OpenLayers....
4
votes
4answers
2k views

How to import polygons from OSM to QGIS?

I am trying to import Polygons from OSM to QGIS 2.0, but so far I have no idea how to do that. E. g.: Kisterseg auf Tatabanya in HU: http://www.openstreetmap.org/?relation=1027806 Is there any fast ...
2
votes
1answer
528 views

Merge Two Polygons Using Editor merge in arcGis

i want to create a ArcEngine function using .net that allow to do the same thing like (see picture): select 2 polygons click merge Is there somebody who can help please!! Sincerely
2
votes
1answer
628 views

Convert polygons to KML file

I have a set of polygons out of which I want to make a KML file, my table schema is as follows : CREATE TABLE [dbo].[utilitygeo]( [ID] [int] NOT NULL, [PolygonID] [varchar](8000) NULL, [...
0
votes
1answer
94 views

Openlayers selection

Is it possible to select a polygon from a predefined Lat & Lon programmatically? eg location point: x='1234' y='5678' intersects polygon '1234', therefore SELECT POLYGON '1234' So far I have ...
1
vote
1answer
583 views

Intersection of multi-polygons in postgis

How can I get the intersection of 3 multi-polygons in postgis? I have three geometry collection and I want a fourth with the result of intersection of the other three. GEOMETRYCOLLECTION(MULTIPOLYGON(...
1
vote
1answer
89 views

What is the best public geoservice for getting data about buildings?

What is the best public geoservice for getting data about buildings, which is free? Or maybe it's better to ask "does exist such a public service?" I want to add some 3d polygons to my 3d plane, ...
0
votes
0answers
48 views

Polygon shading is darker in certain areas

When drawing in qgis i am encountering an error when drawing large polygons snapped to multiple points. Polygons that have this shading in certain areas are not displaying correctly in other ...
1
vote
0answers
142 views

Free cartographic texture resources

I've been trying without success to find free textures to use in TileMill. I'm looking for fairly simple, abstract textures, like a dotted pattern (to indicate national parks). Are there any well ...
2
votes
1answer
725 views

QGIS: CSV point grid to polygon - not raster

I have a CSV file with various data in 1 degree wide by 0.5 degree high rectangles, for which I have the N,S,E,W, & centroid lat/longs, i.e. every bit of spatial data required. I'm trying to ...
7
votes
2answers
5k views

Dissolve polygons in QGIS (GEOS) with tolerance

I have a polygon vector layer representing the area inundated in a flood. The layer has been produced in a such a way that some of the areas are composed of multiple smaller touching polygons (see ...
1
vote
2answers
582 views

how to set width & height of a polygon in QGIS

I can't setting width and height of a polygon How to do that in QGIS? Thank you
2
votes
2answers
2k views

How many interior and exterior rings can a polygon have in a standard ArcGIS shapefile?

working with GDAL/OGR library and studying these two slides about geometries and vector data in the OGR library: slide 1 slide 2 I found that a polygon can have an exterior ring and lots of ...
1
vote
2answers
226 views

Integrate grid and polygon of municipalities keeping the biggest municipality per cell with QGIS (or another)

I have a 9x9 grid and a polygon of municipalities of an extensive area of Brazil. My goal is to have a field indicating the biggest municipality per grid cell. I've been trying with intercept without ...
7
votes
1answer
217 views

Find and destroy duplicate OSM multipolygon/polygons in TileMill/PostGIS

In OpenStreetMap there are sometimes multipolygons where attributes are present on both the polygon and the multipolygon relation, such as the Grampians National Park: http://www.openstreetmap.org/...
1
vote
0answers
119 views

level of spatial aggregation of polygons

I am looking for a method that allows me to obtain the spatial aggregation of polygons for each cell of a grid with 10kmx10km resolution. In each cell (10kmx10km), I want to be able to consider that ...
1
vote
0answers
298 views

Divide polygon based on points for even distribution

If I have a point layer, how can I create a polygon that includes all of the points and divide that polygon into n sections in which each section contains an equal number of points? Preferably in QGIS,...
3
votes
2answers
856 views

Finding points along a path

I am unsure of the best approach to this problem. I can think of some ways of doing it which I will list below but I am looking for the best and most efficient way of doing this. Problem Given a ...
2
votes
1answer
366 views

Split polygon into lines

I have a polygon layer which looks like this . I used the QGIS multiparts to singleparts tool and also polygon to lines. In both cases i got this type of result . I want to extract polygon into ...
1
vote
0answers
181 views

Convert polygon feature to line feature

I have a polygon shape-file i need to extract the line segments where the polygon features intersect each other and also the segment where they don't. Can we automate this process or can scripting ...
6
votes
1answer
331 views

Select by location of doughnut hole polygon

I have vectorized the Corine Land class raster and want to select certain classes that are "inside" other classes. How can I select the polygons circled in blue? All the select by location options ...
1
vote
1answer
284 views

How to get a centroid of a closed line in MYSQL

I have a table that contains only closed lines (lines where endpoint is the same as startpoint). I would need to find a centroid for those lines. How would I be able to achieve it? It does not need,...
1
vote
1answer
347 views

How to get average polygon? [duplicate]

Is there a way to get an average polygon of unioned stack of polygons in ArcGIS 10.0? I would like to get an average polygon that would be centroid (but polygon) of whole stack of polygons.
0
votes
1answer
64 views

represent multiple geometry as single feature

There is a school. it is on two disjoint areas, one is primary wing and other is secondary. I need to make single feature from the two areas such that, there is only one column in gis table, i.e. only ...
1
vote
1answer
1k views

Polygon to raster without losing any polygons

I'm trying to convert polygons to raster. But the output raster dataset doesn't have polygons which went into as input data. I need all the date in the attribute to follow with to the raster dataset ...
1
vote
1answer
826 views

Failed to convert polygon to raster

I have two steps here. First select layer by attributes. Second convert polygon to raster. It failed when it goes to second step and kept giving me error 999999: Error executing function. I pasted my ...
0
votes
1answer
205 views

How to send polygon data to wms?

I use OpenLayers and GeoServer. I can read kml file format from OpenLayers. And I want to edit this polygon in kml. So I want polygon data(polygon circle and center coordinate etc..) to GeoServer.
2
votes
3answers
918 views

Iterating polygons on a SpatialPolygonsDataFrame in R with readWKT

I have fetched some data (39 objects) from my PostGIS database and converted this data into a matrix: rs <- dbSendQuery(con, "SELECT ST_AsText(polygon_accumulation) AS ShapeWKT from accumulation;")...
2
votes
1answer
628 views

Why is field calculator returning NULL for $x and $y in line and polygon layers?

I am trying to include XY coordinates in the attribute tables of several of my vector files; they are line and polygon files. I have tried two methods; first I used $x and $y in the field calculator (...
4
votes
1answer
833 views

Merging partially overlapping polygons into a table in PostGIS

I have a couple of tables (three) with polygons (landuse coverage in this case). Within each table, there is no overlap, but between tables there might be a lot of overlap. I would like to combine ...
0
votes
1answer
465 views

How to convert OSM polyline data to polygons?

I just now downloaded OSM data .I am having the data as polylines. I want that polylines as polygons is it possible in Qgis?below I also posted the screen shot of the polyline also.
3
votes
2answers
130 views

Determining closest representation of polygon as collection of points+radii

Have a bit of a tough question, which I realize there may not be an easy solution to. Figured what better place to ask. I'm attempting to transform a polygon into a series of arbitrary points with ...
0
votes
2answers
745 views

ArcGIS 10.1 - Using Polygon Neighbors with dissolved polygons

I've used polygon neighbors to find all neighbors of a polygon layer, which I then use to look up all possible neighbor combinations and dissolve the polygons into all possible combinations of two ...
1
vote
1answer
683 views

identify percentage of raster cells within a polygon

As per the title I want to determine the population inside multiple polygons according to different land use zoning (High Residential, Low Residential, National Parks etc) that's in raster format. ...